Membrane separation equipment

ABSTRACT

A canister type container for housing semi-permeable membrane cartridge separation units and which canister comprises an enclosed casing wherein a plurality of the cartridge separation units are detachably secured to the inner walls of the casing in parallel-series relationship. Circulation means are provided within the housing for circulating a carrier liquid having a product to be separated therefrom across the surfaces of the membranes for effecting the separation of the product from the carrier liquid.

United States Patent [191 Hubbard et al.

[ MEMBRANE SEPARATION EQUIPMENT [75] Inventors: Peter J. Hubbard, Darien; Eric L. Sandstrom, Bethel, both of Conn.

[73] Assignee: Dorr-Oliver Incorporated, Stamford,

Conn.

[22] Filed: May 3, 1973 [21] Appl. No.: 356,727

[52] US. Cl. 210/197; 210/416; 210/433; 210/456 [51] Int. Cl. ..B01D 31/00 [58] Field of Search 210/321, 416, 433, 456, 210/194, 195, 197, 462, 23, 232

[56] References Cited UNITED STATES PATENTS 1,153,282 9/l9l5 Zahm 2101462 2,956,070 10/1960 Jennings et al. 3,367,787 2/1968 Thijssen et al 210/22 X [4 1 July 8, 1975 3,369,667 2/1968 Clark et 210/194 X 3,457,170 7/l969 Havens 210/23 3,708,069 1/1973 Clark 210/321 X Primary Examiner-Frank A. Spear, Jr. Attorney, Agent, or FirmBurtsell J. Kearns; Harold M. Snyder [5 7] ABSTRACT A canister type container for housing semi-permeable membrane cartridge separation units and which canister comprises an enclosed casing wherein a plurality of the cartridge separation units are detachably secured to the inner walls of the casing in parallel-series relationship. Circulation means are provided within the housing for circulating a carrier liquid having a product to be separated therefrom across the surfaces of the membranes for effecting the separation of the product from the carrier liquid.

11 Claims, 11 Drawing Figures PKTENTEDJIJL 8 ms SHEET 2 3.920

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iATENTEDJUL 8 ms \llllll PATENTEHJUL a ram SHEET Mill FTFW

MEMBRANE SEPARATION EQUIPMENT BACKGROUND OF THE INVENTION The present invention relates to new and useful improvements in semi-permeable membrane separation equipment and in particular to means for housing and mounting membrane separation units in operative relationship within a casing.

In general use semi-permeable membrane separation units or cartridges are arranged within a casing or module assembly and function to separate a selected prod uct or products from a carrier liquid fed to the separation unit. In one mode of use a pressure differential is maintained across the membrane surface as the product carrying liquid is fed under pressure across one side of the membrane surface. Liquid and selected dissolved solids are passed through pores in the membrane surface as a permeate product to a discharge outlet in the casing. The carrier liquid that is not passed through the membrane becomes concentrated with solids and which solids in certain processes is the product until a selected concentration level of solids is reached. The concentrated liquid is then drawn out of the casing and transmitted either to waste or returned to the process in accordance with the predetermined objectives of the particular separation process. Alternatively the permeate may be wasted, returned to process or otherwise utilized.

Membrane separation equipment of the general type mentioned is used in a wide variety of reverse osmosis and ultrafiltration processes. Among other presently well known uses of this equipment, but not limited thereto, are the processing of paint in electrodeposition processes; treatment of waste water; desalination processes, and in food processing such as the treatment of cheese whey.

In this equipment a variety of structures or cartridge assemblies have been used for supporting the membranes. lt one type the membranes are formed on porous surfaces and wound into a spiral tube through which the carrier liquid is transmitted. In other units the membrane separation units are tubular in shape. Still another type cartridge unit is disclosed in U.S. Pat. No. 3,494,465 and includes porous sheets mounted on a supporting plate with the membranes formed on both sides of the porous sheets. The permeate passes through the membrane to the porous sheet and is then fed to the supporting plate. Specially designed casing structure is provided for housing these cartridges and which structure is complementary with the supporting plate for receiving the permeate. The casings are also provided with suitable outlets for the permeate output flow and the concentrated carrier liquid output.

In these known units the surface area available for membrane filtration is limited by the specially formed casing construction and cartridge structure. As a result the capability of external pump capacity for circulating the carrier liquid through the casing is also limited. In addition to the reduced separation capacity as the membrane surface area is reduced, there is a corresponding decrease in the volume of carrier liquid that can be processed through the unit. In known casings difficulties are also present in providing ready access to the cartridges for inspection and replacement. The latter problems are further complicated by the relatively complex casing structure and specially configurated wall portions for mounting the cartridges and providing suitable permeate outlets and the like.

It is an object of the present invention to provide a novel canister casing for housing semi-permeable membrane cartridges.

Another object is to provide a novel canister for supporting therein a plurality of membrane separation cartridges in parallel-series relationship.

A further object is to provide a canister wherein novel means are provided for circulating carrier liquid through the housing and wherein the overall surface area available for separation is increased while the overall size of the canister housing is reduced.

A still further object is to provide a novel canister wherein means are provided for permitting ready access to the separation cartridges and further include means for allowing ready removal and replacement thereof from the canister housing.

SUMMARY OF THE INVENTION The present invention comprehends a novel canister casing for housing therein cartridges supporting semipermeable membrane separation surfaces in parallelseries relationship. In one embodiment the canister comprises a generally rectangular shaped pressurized casing with the separation cartridges arranged on the inner walls of the casing in banks of parallel-series relationships. Ready releasable attaching means are provided for locating and securing the cartridges to the sidewalls of the casing. Circulation means including a centrally disposed impeller pump are provided in the casing for circulating a carrier liquid supplied to the canister across the membrane surfaces whereby a selected product is removed from the liquid as a permeate passing through the membrane surface. Flow directing means are arranged within the casing for controlling and properly channeling the circulating liquid from and between the pump means and cartridge surfaces. In a further embodiment there is provided a canister having an unpressurized housing with the circulation means depending from and detachably mounted on the housing cover.

The above and other advantages of the present invention will appear more fully hereinafter from a consideration of the detailed description which follows taken together with the accompanying drawings wherein two embodiments of the invention are illustrated.

DESCRIPTION OF THE DRAWINGS In the Drawings:

FIG. 1 is a front elevational view. partly shown in section, of a canister which houses semi-permeable membrane separation units and in which is incorporated one embodiment of the present invention;

FIG. 2 is a sectional view taken on line 2-2 of FIG.

FIG. 3 is a perspective view of the canister of FIG. 1 with the cover removed;

3 FIG. 4 is a top plan view of the canister shown in FIG.

FIG. 5 is an enlarged side elevational view showing one of the membrane separation units secured to a sidewall of the canister housing;

FIG. 6 is a sectional view taken on line 6-6 of FIG.

FIG. 7 is a perspective view of a membrane separation cartridge;

FIG. 8 is a front elevational view partly shown in section, of an alternate embodiment of the present invention;

FIG. 9 is a sectional view taken on line 9-9 of FIG.

FIG. 10 is a front elevational view of the circulation pump assembly of FIG. 8 removed from the canister; and

FIG. 11 is a sectional view taken on line 11ll of FIG. 10.

GENERAL DESCRIPTION OF THE INVENTION Referring now to the drawings for a more detailed de scription of the present invention, a canister which incorporates one embodiment thereof is generally indicated by the reference numeral 12 in FIG. 1 and is shown mounted on a supporting frame 13. A plurality of membrane separation cartridges 15 are secured to the inner walls of canister 12. An input conduit 16 for reception of a carrier fluid is provided at the base of canister 12. A circulation pump 17 driven by a motor 18 for circulating carrier liquid across the membrane surfaces of cartridges 15 is provided within canister 12 whereby a discharge of a permeate through a permeate discharge pipe 19 is effected in a manner to be hereinafter fully described in detail.

Canister 12 (FIGS. 1 and 3) comprise a pressurized steel housing which includes a steel cover 21 and a rectangular shaped steel main lower casing 23. Casing 23 includes spaced sidewalls 24 and a bottom wall 25. The carrier liquid input conduit 16 extends from the exterior of canister 12 through bottom wall 25. In a similar manner a bleed or effluent conduit 27 through which concentrated carrier liquid is withdrawn from canister 12 is provided in cover 21. Vertically spaced hollow channel members 29 are fixed to the outer surface of sidewalls 24 and extend around the outer surface of canister 12. Channel members 29 function to receive permeate from canister 12 which is directed along channel members 29 to a single permeate outlet pipe 19 which is interconnected to all channels 29 and has openings 30 (FIG. 3) in communication therewith.

The lower peripheral edges of cover 21 secured in sealed detachable relationship to main casing 23 by toggle type latch members 32 (shown in latched position in FIG. 1). Suitable sealing strips (not shown) are provided between the adjacent edges of casing 23 and cover 21 to prevent leakage of carrier fluid from canister 12. As will be appreciated cover 21 is readily released from casing 23 to permit access to the interior of canister 12 when toggle latches 32 are moved to an unlatched position.

A bank of vertical compartments 34 (FIGS. 3 and 4) for housing membrane separation cartridges 15 are provided at each sidewall 24 of main casing 23 and which compartments are formed and separated one from the other by metal spacing members 35. A draft tube 36 is provided in casing 23 and comprises a cylindrical shaped conduit supported by spacing members 35. Draft tube 36 extends longitudinally of canister 12 and is open at both bottom wall 25 and cover 21 thereof.

Flow circulating means (FIG. 1) are disposed within draft tube 36 and includes circulation pump 17. Pump 17 comprises an impeller assembly 38 secured to one end of a rotatable shaft 39. Shaft 39 extends from draft tube 36 through bottom wall 25 into a bearing housing 40 on frame 13. Suitable bearing and sealing means (not shown but diagrammatically indicated by reference numeral 41) are provided for shaft 39 at bottom wall 25 to prevent leakage of carrier liquid and provide for proper rotation of shaft 39. A flexible drive belt 43 connects shaft 39 to the rotatable shaft 44 of motor 18 which is also mounted on support frame 13.

Means for controlling and directing the flow of carrier liquid from draft tube 36 to cartridge compartments 34 are provided on cover 21 and bottom wall 25 of casing 23. The flow directing means on cover 21 are identical to the flow directing means provided on bottom wall 25 and description of the components thereof is directed to the means on cover 21. As seen in FIGS. 1 and 2 the flow directing means on cover 21 include a rectangular shaped vane member 46 which is of semicircular cross-sectional configuration (FIG. 1). Vane 46 is suspended from cover 21 by struts 47 (FIG. I) and includes outer and inner legs 48 and 49 (FIGS. 1 and 2). In closed position of cover 21 inner legs 49 are disposed over draft tube 36. The outer legs 48 (FIG. 2) are disposed over the top of the adjacent banks of membrane cartridge compartments 34. Additional curved vane members 50 (FIGS. 1 and 2) of shorter dimension than vane 46 are provided for each cartridge compartment bank. Vane 50 is suspended from strut 50A with the inner leg 51 of each vane disposed over draft tube 36 and the outer leg 50 over the top surfaces of the middle two cartridge compartments 34. As illustrated in FIG. 1 an open circular vane 53 is arranged within tube 36 above the impeller assembly 38.

Membrane cartridges 15 are similar to those disclosed in the mentioned US. Pat. No. 3,494,465. Each cartridge 15 (FIGS. 5, 6 and 7) includes a hollow supporting plate or manifold 54 made of suitable hard plastic material. A plurality of leaf members 55 of suitable porous material such as phenobic treated filter paper are mounted on the bottom wall 56 of manifold 54. The free edge and both faces of each leaf 55 are coated with a semi-permeable membrane 57 having pores of predetermined dimensions in a known manner such as that described in US. Pat. No. 3,508,994 to provide a completed membrane leaf 58. The bottom edge 59 of each porous leaf 55 is uncoated and is open to the hollow interior of the mainfold plate 54. A plurality of plastic spacers bars 61 are provided at intervals on each membrane cartridge 15 and are provided with slots snap fitted over adjacent edges of leaves 58 to maintain the spacing between adjacent membrane leaves 58.

In this manner as fully described in the mentioned patents, as a carrier liquid is passed between the interstitial spaces between membrane leaves 58 a separation of constituents of the liquid is effected. A portion of the liquid with the product dissolved will penetrate through the pores in the membrane surface 57 and pass into porous leaf 55 as a permeate and outwardly from the free edge 59 thereof to collect in the hollow area 60 of manifold 54.

As seen in FIGS. 1, 3 and 4 membrane cartridges 15 are provided in parallel banks of three cartridge compartments 34 at each sidewall 24 of canister 12. Each compartment 34 includes three membrane cartridges 15 arranged in series in space vertical relationship one with the other on one sidewall 24. In this manner in the embodiment of FIGS. 1 to 7 there are provided nine membrane cartridges at each sidewall 24. In one operative design of the disclosed canister embodiment each cartridge has a filter surface of 18 square feet resulting in a total available filtering surface of 162 square feet at each sidewall 24 and a total canister capacity of 648 square feet within a canister area of only 22 cubic feet.

As mentioned it is a feature of this invention to provide novel means for locating and securing cartridge units to sidewall 24. To this end each manifold 54 is provided with a raised boss portion 63 (FIGS. 5-7) mounted in a communicating outlet port opening 64 in sidewall 24 which opens into an adjacent flanged permeate channel 29 on the outer surface of canister 12. Permeate transmitting plug members 65 are provided with a first threaded portion 66 threaded into boss portion 63. An outer detachable cap member 68 extends through an opening 69 in permeate channel 29 and is in turn threaded about a second threaded portion 69 of plug 65. Suitable O-rings 73 are provided at the aligned openings 64 and 69 in the sidewall 24 and channel 29 to prevent leakage of permeate from canister 12. A permeate opening 75 is provided in manifold 54 in alignment with a central conduit 76 in permeate plug 65. Conduit 76 opens to the interior of the permeate channel 29. A suitable check valve 78 is provided in plug 65 within conduit 76 (diagrammatically shown in FIG. 5) to prevent reverse flow of permeate to mani fold 54.

In this manner membrane cartridges may be readily attached or detachably secured to sidewall 24 as desired. If it is desired to remove a cartridge 15 from canister 12, cover 21 is first removed from main casing 23. Cap 68 of the selected cartridge 15 is unthreaded from plug 65. A finger piece 79 on plug 65 is then rotated to release plug 65 from manifold 54 and in turn the cartridge from the sidewall 24.

In use of the canister assembly the input, bleed and permeate conduits are connected to suitable piping of the particular process used. A supply of carrier liquid is fed to canister from the selected process (not shown) through input tube 16 at a high flow rate to maintain a ratio of feed to permeate effluent in a range of 3 to l as high as 50 to I. In one process use the canister of FIGS. 1 to 7 has been found suitable for food processing such as the treatment of cheese whey. As the feed or carrier liquid enters the draft tube 36 pump 17' is operated to circulate the feed material upwardly through the adjacent membrane cartridge compartments 34 as indicated by the directional arrows in FIG. 1. As the carrier liquid passes over the membrane surfaces a preselected separation of selected constituents in accordance with the preselected size of the membrane pores and requirements of the particular process is effected.

As a result of the fluid pressure differential existing between the interlaminate spaces of the membrane leaves 58 and interstitial spaces between adjacent leaves 58, certain carrier liquid and dissolved constituents pass as a permeate into leaves 58 and thence to manifold plate 54 and outwardly of canister 12 through the permeate plug 65. The carrier liquid that does not pass through the membrane surfaces becomes concentrated with unpassed solids and is released as needed from canister 12 through effluent pipe 27.

As the concentrated flow leaves and enters compartments 34 it engages the flow directing means. Vanes 46 and 50 assure a proper circulation flow from the draft tube 36 to compartments 34 by controlling and turning the flow as indicated by the directional arrows in FIG. 1 into draft tube 36 from compartments 34 at cover 21 and from the draft tube 36 into compartments 34 at bottom wall 25. As mentioned when a selected concentration level is reached in the concentrate liquid the concentrate is bled from canister 12 through effluent tube 27 and wasted or returned to the process flow. The permeate collected in outer channel members 29 is drawn outwardly from channels 29 through permeate tube 19 by suitable external pump means (not shown).

In FIGS. 8 to 11 inclusive is shown in a further embodiment of the present invention wherein the modification of the canister and flow circulation means is illustrated as applied to an unpressurized canister housing 80. In FIGS. 8 to II corresponding reference numerals have been applied in certain instances to like elements previously described for the first embodiment.

As seen in FIG. 8 the pump assembly 81 is mounted on the upper cover 82 of canister 80. To this end cover 82 is provided with an opening 83 through which depends the circulation pump 81. Circulation pump 81 includes an outer bearing housing 84 having a bottom wall portion 86 seated on the surface of cover 82 and secured thereto by detachable latch members 88. Suitable sealing means (not shown) are provided between adjacent parts of cover 82 and wall portion 86 about opening 83 to prevent leakage of carrier liquid from canister 80. Shaft 89 extends into draft tube 90 and is provided with a propeller assembly 91. Shaft 89 is rotated by a drive belt 43 from drive motor (not shown).

Spaced flow directing fins 92 extend from a funnelshaped plate 96 depending from bottom wall 86 of bearing housing 84. The lower portion of fins 92 are secured to a stiffening rim member 93 (FIGS. 10 and 11).

Membrane cartridges 15 in FIGS. 8 to 11 inclusive are identical to those described in the previous embodiment and are secured to the sidewalls 24 of canister 86 in an identical manner. In a like manner the carrier liquid input conduit 16 is provided on the outer sidewalls of canister 80. A bleed or effluent pipe 27 is located in cover 82 in a similar manner. The flow directing means on cover 82 differ from that previously described in that only a single wall vane surface 95 is provided on cover 82 (FIGS. 8 and 9) and cooperate with the outer surface of funnel plate 96 and fins 92 in directing the flow from cartridge compartments 34 to draft tube 96 as indicated by the directional arrows in FIG. 8.

As will be readily appreciated the structural arrangement of canister 80 permits ready removal of both the pump assembly 81 and cartridges 15 thereby permitting easy access to all parts of the canister for repair, cleaning or replacement.

It will be further apparent from the foregoing description that the novel canister and membrane cartridge arrangements disclosed have many advantages in use. Among other advantages is that increased filtration area and availability of membrane surface is provided within the disclosed canisters within a lesser casing area than previously achieved. The means for mounting the cartridge units on the sidewalls provide for increased circulation flow across the surfaces and allow for ready replacement of cartridges for cleaning or replacement or the like. The fact that the inner surfaces of the casing sidewall are not formed with complicated recesses, drainage channels or the like allows for increased recirculation of the concentrated liquid within the canister greatly reducing clogging of interior spaces with solids or the like.

Further advantages of the described canister is the versatility thereof that they can be operated in varying processes. In the unpressurized housing an extraction pump can be used to provide pressure drops across the membrane surfaces by evacuating the permeate side of the membrane and using a feed pump to supply carrier liquid and bleed at minimal pressure. In a pressurized unit a feed pump is used to supply feed, bleed and operating pressure drops across the membrane surface or in combination with an extraction pump.

Although only two embodiments of the present invention have been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design and arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

1. Apparatus for housing in operative relationship a plurality of individual ultrafiltration separation units each having a plurality of semi-permeable membrane surfaces for separating solids from a carrier liquid fed to said apparatus, said apparatus comprising:

a. an enclosed casing having inner and outer sidewall surfaces,

b. inlet means for receiving the carrier liquid and outlet means for discharging a concentrated solution both provided on said casing,

c. means mounting said separation units in spaced relationship within said casing upon said inner sidewall surfaces,

d. permeate outlet means extending from each of said separation units through said casing sidewalls,

e. liquid circulation and solids concentrating means provided within said casing for directing said carrier liquid fed to said casing across the membrane surfaces of said separation units,

f. said circulation and solid concentrating means including an open circulation conduit provided within said casing and spaced from said separation units for providing an uninterrupted flow path for the carrier liquid and pump means within said conduit operable to direct said carrier liquid through said conduit and across the membrane surfaces of all of said separation units, said pump means further operable to recirculate the carrier liquid containing said concentrated solids through the open circulation conduit in a continuous path until a selected concentrated solids level is effected.

2. Apparatus for housing in operative relationship a plurality of individual ultrafiltration units each having a plurality of semi-permeable membrane surfaces for separating solids from a carrier liquid fed to said apparatus, said apparatus comprising:

a. an enclosed casing including a bottom wall, spaced opposite sidewalls and a removable cover,

b. inlet means for receiving the carrier liquid and outlet means for discharging a concentrated carrier liquid solution both provided on said casing,

c. a bank of at least two separation units mounted in series relationship on each of said opposite inner sidewall surfaces of said casing,

d. permeate outlet means on each of said units for permitting individual discharge of permeate from said casing from each unit,

e. an open circulation conduit provided in said casing and arranged between said banks of separation units for providing an uninterrupted flow path for the carrier liquid,

f. liquid circulation and solid concentration means arranged within said casing adjacent said banks of separation units and circulation conduit, said latter means including pump means in said circulation conduit for directing said carrier liquid fed to said conduit across the membrane surfaces of said banks of separation units and for circulating said carrier liquid through said circulation conduit in a continuous return path to said separation units until a selected concentrated solids level is effected.

3. The device of claim 2 wherein flow directing and turning means for controlling the flow of carrier liquid in the circulation path between said separation units and circulation conduit are provided within said casing and include vane members on said casing cover and bottom wall, said vane members having portions in alignment with said separation units and with said circulation conduit for receiving and controlling the flow of carrier liquid from and between said separation units and circulation conduit.

4. The device of claim 3 wherein said flow directing vane members each include a channel member of semicircular cross-section configuration, a first leg of said vane positioned adjacent said separation unit and the other leg adjacent said circulation conduit,said vane member adapted to receive the flow of carrier liquid in the circulation path and direct the flow from and between the separation units and circulation pump.

5. The device of claim 4 wherein an opening is provided in said cover, said pump including a shaft and impeller assembly depending into said draft tube through said opening, and means detachably mounting said pump on said cover.

6. The device of claim 2 wherein said circulation conduit comprises a central draft tube and wherein said pump circulation means includes an impeller pump disposed within said draft tube and operable to pump and circulate said carrier liquid in the recirculation path through said draft tube and adjacent separation units.

7. The device of claim 2 wherein said casing is of a rectangular configuration in horizontal cross-section and wherein separation units are mounted on each of said inner sidewalls with said circulation conduit extending coaxially therebetween.

8. The device of claim 7 wherein a plurality of channel members are provided on the outer sidewall surface of said casing for receiving the permeate from said permeate outlet means, and a single permeate output conduit interconnected to all of said channel members for receiving the accumulated permeate from all of the separation units.

9. The device of claim 7 wherein said separation units each comprise a plurality of porous leaf members mounted on a manifold support member, said membrane surfaces provided on said porous leaves for separating a permeate from the carrier liquid for transmission to said permeate outlet means, said leaves adapted to receive the permeate from said member and transmit the permeate to the manifold support member, and means mounting said support on said casing sidewall means, and said manifold having an opening in communication with said permeate outlet means.

10. The device of claim 7 wherein at least two separation units are provided on each of said inner sidewalls 10 in parallel circuit relationship one with the other wherein said circulation means is operable to circulate the carrier liquid in a circulation path through said separation units in parallel.

* a: t a: 

1. APPARATUS FOR HOUSING IN OPERATIVE RELATIVE RELATIONSHIP A PL URALITY OF INDIVIDUAL ULTRAFILRATION SEPARTION UNITS EACH HAVING A PLURALITY OF SEMI-PERMEABLE MEMBRANE SURFACES FOR SEPARATING SOLIDS FROM A CARRIER LIQUID FED TO SAID APPARATUS, SAID APPARATUS COMPRISING: A. AN ENCLOSED CASING HAVING INNER AND OUTER-SIDEWALL SURFACES, B. INLET MEANS FOR RECEIVING THE CARRIER LIQUID AND OUTLET MEANS FOR DISCHARGING A CONCENTRATED SOLUTION BOTH PROVIDED ON SAID CASING. C. MEANS MOUNTING SAID SEPERATION UNITS IN SPACED RELATIONSHIP WITHIN SAID CASING SEPARATION UNITS IN SPACED RELATIOND. PERMEATE OUTLET MEANS EXTENDING FROM EACH OF SAID SEPARATION UNITS THROUGH SAID CASING SIDEWALLS, E. LIQUID CIRCULATION AND SOLIDS CONCENTRATING MEANS PROVIDED WITHIN SAID CASING FOR DIRECTING SAID CARRIER LIQUID FED TO SAID CASING ACROSS THE MEMBRANE SURFACES OF SAID SEPARATION UNITS. F. SAID CIRCULATION AND SOLID CONCENTRATING MEAS INCLUDING AN OPEN CIRCULATION CONDUIT PROVIDED WITHIN SAID CASING AND SPACED FROM SAID SEPARATION UNITS FOR PROVIDING AN UNINTERRUPTED FLOW PATH FOR THE CARRIER LIQUID AND AND PUMP MEANS WITHIN SAID CONDUIT AND ACROSS THE MEMBRANE LIQUID THROUGH SAID CONDUIT AND ACROSS THE MEMBRANE SURFACES OF ALL SAID SEPARATION UNITS, SAID PUMP MEANS FURTHER OPERABLE TO RECIRCULATE THE CARRIER LIQUID CONTAINING SAID CONCENTRATED SOLIDS THROUGH THE OPEN CIRCULATION CONDUIT IN A CONTINUOUS PATH UNTIL A SELECTED CONCENTRATED SOLIDS LEVEL IS EFFECTED.
 2. Apparatus for housing in operative relationship a plurality Of individual ultrafiltration units each having a plurality of semi-permeable membrane surfaces for separating solids from a carrier liquid fed to said apparatus, said apparatus comprising: a. an enclosed casing including a bottom wall, spaced opposite sidewalls and a removable cover, b. inlet means for receiving the carrier liquid and outlet means for discharging a concentrated carrier liquid solution both provided on said casing, c. a bank of at least two separation units mounted in series relationship on each of said opposite inner sidewall surfaces of said casing, d. permeate outlet means on each of said units for permitting individual discharge of permeate from said casing from each unit, e. an open circulation conduit provided in said casing and arranged between said banks of separation units for providing an uninterrupted flow path for the carrier liquid, f. liquid circulation and solid concentration means arranged within said casing adjacent said banks of separation units and circulation conduit, said latter means including pump means in said circulation conduit for directing said carrier liquid fed to said conduit across the membrane surfaces of said banks of separation units and for circulating said carrier liquid through said circulation conduit in a continuous return path to said separation units until a selected concentrated solids level is effected.
 3. The device of claim 2 wherein flow directing and turning means for controlling the flow of carrier liquid in the circulation path between said separation units and circulation conduit are provided within said casing and include vane members on said casing cover and bottom wall, said vane members having portions in alignment with said separation units and with said circulation conduit for receiving and controlling the flow of carrier liquid from and between said separation units and circulation conduit.
 4. The device of claim 3 wherein said flow directing vane members each include a channel member of semi-circular cross-section configuration, a first leg of said vane positioned adjacent said separation unit and the other leg adjacent said circulation conduit, said vane member adapted to receive the flow of carrier liquid in the circulation path and direct the flow from and between the separation units and circulation pump.
 5. The device of claim 4 wherein an opening is provided in said cover, said pump including a shaft and impeller assembly depending into said draft tube through said opening, and means detachably mounting said pump on said cover.
 6. The device of claim 2 wherein said circulation conduit comprises a central draft tube and wherein said pump circulation means includes an impeller pump disposed within said draft tube and operable to pump and circulate said carrier liquid in the recirculation path through said draft tube and adjacent separation units.
 7. The device of claim 2 wherein said casing is of a rectangular configuration in horizontal cross-section and wherein separation units are mounted on each of said inner sidewalls with said circulation conduit extending coaxially therebetween.
 8. The device of claim 7 wherein a plurality of channel members are provided on the outer sidewall surface of said casing for receiving the permeate from said permeate outlet means, and a single permeate output conduit interconnected to all of said channel members for receiving the accumulated permeate from all of the separation units.
 9. The device of claim 7 wherein said separation units each comprise a plurality of porous leaf members mounted on a manifold support member, said membrane surfaces provided on said porous leaves for separating a permeate from the carrier liquid for transmission to said permeate outlet means, said leaves adapted to receive the permeate from said member and transmit the permeate to the manifold support member, and means mounting said support on said casing sidewall means, and said manifold having an opening in communication with said Permeate outlet means.
 10. The device of claim 7 wherein at least two separation units are provided on each of said inner sidewalls in series circuit relationship one with the other and wherein said circulation means is operable to circulate the carrier liquid simultaneously through said separation units.
 11. The device of claim 7 wherein at least two separation units are provided on each of said inner sidewalls in parallel circuit relationship one with the other wherein said circulation means is operable to circulate the carrier liquid in a circulation path through said separation units in parallel. 